3D audio commonly refers to a series of signal processing, transmission, encoding, and playback techniques for providing a sound which gives a sense of presence in a three-dimensional space by providing an additional axis corresponding to a height direction to a sound scene on a horizontal plane (2D) provided by conventional surround audio. In particular, 3D audio requires a rendering technique for forming a sound image at a virtual position where a speaker does not exist even if a larger number of speakers or a smaller number of speakers than that for a conventional technique are used.
3D audio is expected to become an audio solution to an ultra high definition TV (UHDTV), and is expected to be applied to various fields of theater sound, personal 3D TV, tablet, wireless communication terminal, and cloud game in addition to sound in a vehicle evolving into a high-quality infotainment space.
Meanwhile, a sound source provided to the 3D audio may include a channel-based signal and an object-based signal. Furthermore, the sound source may be a mixture type of the channel-based signal and the object-based signal, and, through this configuration, a new type of listening experience may be provided to a user.
Binaural rendering is performed to model such a 3D audio into signals to be delivered to both ears of a human being. A user may experience a sense of three-dimensionality from a binaural-rendered 2-channel audio output signal through a headphone or an earphone. A specific principle of the binaural rendering is described as follows. A human being listens to a sound through two ears, and recognizes the location and the direction of a sound source from the sound. Therefore, if a 3D audio can be modeled into audio signals to be delivered to two ears of a human being, the three-dimensionality of the 3D audio can be reproduced through a 2-channel audio output without a large number of speakers.
However, a human being may recognize the direction and the level of a sound not only through the sound but also through a vibration generated due to the sound. Therefore, such a vibration also significantly affects human being's recognition of three-dimensionality of a sound. Therefore, if a binaural rendering audio signal processing device gives an additional stimulation to a user together with binaural rendering, the binaural rendering audio signal processing device may improve three-dimensionality perceived by a user through binaural rendering.